This invention relates to weapon aiming systems such as those used in the fire control system of a military tank.
In a conventional optical aiming system for use with a weapon which is angularly moveable, typically in elevation, there is usually a requirement for the optical relay to the gunner to be positioned remote from the bore-line of the weapon. For example, if the weapon is the gun of a tank, the weapon is usually mounted in the turret, which is itself swivelable in the azimuth plane, the gun also being elevatable. To aim the weapon an optical sighting system is used in which a swivelable mirror is mounted outside the armour level of the turret above the gun and sometimes also to one side of it. The mirror is of necessity required to be rotated at half of the angular velocity of the weapon itself, i.e. the ratio of angular movement between the weapon and the mirror is 2:1.
Known mechanisms for producing such a 2:1 ratio of movement between the weapon and the mirror are usually fairly complicated, in view of the extreme accuracy required, where tolerances of less than about one milliradian are the norm. Examples of such types of mechanism in conventional use utilise in one case a pully and belt drive arrangement and in another case an arrangement which uses a slider crank in conjunction with a slider block. However known conventional arrangements are generally very complicated and/or bulky and are often prone to causing inaccuracies in the sighting system unless they are regularly serviced and adjustments carried out as necessary. The present invention seeks to provide an alternative aiming system which uses a small number of parts but yet still provides a required 2:1 ratio of angular movement between the weapon and the mirror. The invention also seeks as an additional object to provide a weapon aiming system which is particularly compact and can, in suitable circumstances, even be retro-fitted to existing systems.